An internal combustion engine may utilize various types of combustion. For example, spark ignition (SI) of a homogenous mixture during the expansion stroke is one example. This method relies on a timed spark from a sparking plug in order to achieve ignition of an air and fuel mixture within the combustion chamber. Another type of combustion is homogeneous charge compression ignition (HCCI), which occurs when the temperature of the air/fuel mixture within the combustion chamber attains the autoignition temperature of the specific fuel. HCCI can be used to provide greater fuel efficiency and reduced NOx production under some conditions.
In one example approach utilizing HCCI combustion, heat exchangers may be used to extract energy from the exhaust to heat intake air and thereby improve overall thermodynamic efficiency. However, the inventors herein have recognized that during engine cold starting, there may be insufficient exhaust gas energy to generate stable HCCI combustion. Further, cold engine conditions, such as cold engine coolant, can further exacerbate cold starting with HCCI combustion.
As such, in one embodiment, a system for an internal combustion engine, the engine having an intake and exhaust manifold, may be provided. The system comprises: a heat exchanger configured to extract energy from an exhaust gas of the engine; a catalyst coupled between said heat exchanger and the exhaust manifold of the engine; a spark plug in a cylinder of the engine; and a controller to operate the engine to perform spark ignition of a mixture of air and fuel in said cylinder during an engine cold start and/or the warm-up process, where said air is heated with said heat before being inducted into said cylinder.
In this way, it is possible to transfer some of the energy from the exhaust gases to the intake air to further promote rapid warm-up of the engine and catalyst, without limiting exhaust energy available to the catalyst. In other words, the exhaust energy can be used to increase the temperature of an air-fuel mixture in the combustion chamber, thereby improving fuel atomization and thereby enabling increased ignition timing retard. Further, the increase mixture temperature may also increase exhaust gas temperature.